The gamma rays and positrons of --- this is approximately the energy of the 's from pion beta and decays and 's from as explained in chapter 4 --- were thrown into the apparatus according to the stopping distributions and tracked throughout the detector volumes, keeping track of the location of the energy deposition at each step.
Figure: Profiles of the electromagnetic shower spreading in the calorimeter. Shown here are the histograms of the means and FWHM's of the energy deposited by the shower inside a conical fiducial subvolume of the calorimeter. The conical subvolumes are defined by the half-opening angles, . Showers were initiated by photons (solid curves) and positrons (dashed curves) using the Geant simulation package.
The energy deposited was then histogrammed into one degree conical bins concentric with the direction of the original particle's momentum. From figure , it is concluded that:
Therefore, the building blocks of the two main data triggers, and , are overlapping clusters of seven crystals. To each cluster, there corresponds a symmetric one in the opposite hemisphere. The determination of the clusters and their efficiency in detecting the gamma rays and positrons (of ) which indeed deposit over in the calorimeter, have been thoroughly investigated. The threshold of is selected so as to discriminate against the Michel 's whose spectrum extends up to as explained in chapter 4. 's and 's were thrown into the apparatus and the energy deposited into each cluster was recorded. A total of 100,000 shower histories were collected for each type of particles. The vetoes, due to their role as shower vetoes, are not included in the clustering scheme. In addition, a given module cannot belong to more than three clusters: this avoids the degradation of the PMT signals due to excessive splittings. The efficiency of the clustering scheme in detecting the particles whose shower energies exceed the threshold was defined as follows: